Roots of a plant plays important roles, such as nutritional absorption and anchoring a plant body upright. However, many of the factors associated with such physiological phenomena remain unknown.
Recently, a method called FOX hunting system has been developed, by which genes whose DNA sequences have been determined but functions have not been understood yet can be comprehensively analyzed (JP Patent Publication No. 2003-018808 A). In this system, full-length cDNA is linked to a high-expression vector and the vector thus obtained is introduced into Arabidopsis thaliana, whereby Arabidopsis thaliana highly-expressing the full-length cDNA is produced. The FOX hunting system described as above is applicable to various genetic analyses.
On the other hand, some patent applications relating to the growth of a plant have been filed, and examples thereof include those relating to a gene-controlling extension of plant roots (JP Patent Publication No. 2004-187564 A), a method for promoting the growth of a plant (JP Patent Publication No. 2004-305051 A), and a method for increasing the growth of a plant and crop yield (JP Patent Publication No. 2002-531083 A). JP Patent Publication No. 2004-187564 A discloses that an Arabidopsis thaliana gene specifically expressed in root tips (AtGCN20-3) was identified utilizing Arabidopsis thaliana T-DNA tag lines. JP Patent Publication No. 2004-305051 A discloses that extension of growing organs such as roots is promoted by over-expression of a plant-derived cyclin B2 gene. JP Patent Publication No. 2002-531083 A discloses that a plant is transformed with a nucleic acid encoding a cyclin protein that is linked to regulatory sequences to produce a transformed plant exhibiting increased growths of roots and shoots.